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CN-121983670-A - Electrolyte additive, nonaqueous electrolyte and secondary battery

CN121983670ACN 121983670 ACN121983670 ACN 121983670ACN-121983670-A

Abstract

The invention discloses an electrolyte additive, a nonaqueous electrolyte and a secondary battery, wherein the electrolyte additive comprises a first additive, a second additive and a third additive, the first additive is lithium salt containing a fluorine sulfonyl structure, the second additive is a compound containing a sulfonyl structure, and the third additive is a compound containing two or more sulfate ring structural units. Through the synergistic effect of the multi-component additives, an interfacial film with a differential characteristic can be constructed in situ at an electrode interface, so that the high-voltage cycling stability is improved, the side reaction of the interface is reduced, the low-temperature dynamics is optimized, and the rate capability is improved. The invention further discloses a nonaqueous electrolyte containing the electrolyte additive and a secondary battery using the nonaqueous electrolyte.

Inventors

  • ZHU XINGYU
  • Li Zhaoyirou
  • YANG RUI

Assignees

  • 深圳泰科聚能新能源材料有限公司

Dates

Publication Date
20260505
Application Date
20260407

Claims (18)

  1. 1. The electrolyte additive is characterized by comprising a first additive, a second additive and a third additive, wherein the first additive is a lithium salt containing a fluorine sulfonyl structure, the second additive is a compound containing a sulfonyl structure, and the third additive is a compound containing at least two sulfate ring structural units.
  2. 2. The electrolyte additive of claim 1, wherein the first additive is selected from at least one of lithium fluorosulfonate, lithium trifluoromethane sulfonate, lithium bis (trifluoromethane sulfonyl) imide, and lithium bis (trifluoromethane sulfonyl) imide.
  3. 3. The electrolyte additive according to claim 1, wherein the second additive is a compound containing a sulfonyl fluoride structure.
  4. 4. The electrolyte additive of claim 3, wherein the second additive has a structure as shown in formula (I): (formula I); R 1 is selected from hydrogen, C 1 –C 6 alkyl, fluoro C 1 –C 6 alkyl or cyano-substituted C 1 –C 6 hydrocarbyl, and R 2 is selected from hydrogen, C 1 –C 6 alkyl or fluoro C 1 –C 6 alkyl.
  5. 5. The electrolyte additive of claim 3 wherein the second additive is preferably one or more of N, N-dimethyl sulfonyl fluoride, N-methyl-N-ethyl sulfonyl fluoride, N-dicyanosulfonyl fluoride.
  6. 6. The electrolyte additive of claim 1 wherein the third additive is a compound comprising at least two 1,3, 2-dioxathiolane-2, 2-dioxide structural units.
  7. 7. The electrolyte additive of claim 1, further comprising a fourth additive, the fourth additive being an interface-modulating additive.
  8. 8. The electrolyte additive of claim 7 wherein the fourth additive is selected from at least one of lithium difluorooxalato borate, lithium bisoxalato borate, ethylene carbonate additives, fluoroethylene carbonate, 1, 3-propane sultone, 1,3, 2-dioxathiolane-2, 2-dioxide.
  9. 9. A non-aqueous electrolyte comprising the electrolyte additive of any one of claims 1-8, at least one primary lithium salt, and at least one non-aqueous organic solvent.
  10. 10. The nonaqueous electrolytic solution according to claim 9, wherein the mole percentage of the first additive is 0.01 to 0.5% based on 100% of the sum of the molar amounts of the main lithium salt and the first additive.
  11. 11. The nonaqueous electrolytic solution according to claim 9, wherein the mass percentage of the second additive is 0.05 to 3.0% based on 100% of the total mass of the nonaqueous electrolytic solution.
  12. 12. The nonaqueous electrolytic solution according to claim 9, wherein the third additive is 0.05 to 2.0% by mass based on 100% by mass of the total nonaqueous electrolytic solution.
  13. 13. The nonaqueous electrolytic solution according to claim 9, wherein the main lithium salt is at least one selected from the group consisting of lithium hexafluorophosphate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide, and lithium difluorooxalato borate.
  14. 14. The nonaqueous electrolyte according to claim 9, wherein the concentration of the main lithium salt is 0.5 to 2.0 mol/L.
  15. 15. The nonaqueous electrolyte according to claim 9, wherein the nonaqueous organic solvent comprises at least one of a carbonate solvent selected from the group consisting of ethylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate and propylene carbonate, a carboxylate solvent selected from the group consisting of at least one of methyl acetate, ethyl formate, ethyl acetate, propyl propionate, ethyl propionate and propyl acetate, and an ether solvent selected from the group consisting of at least one of ethylene glycol dimethyl ether and diethylene glycol dimethyl ether.
  16. 16. The nonaqueous electrolytic solution according to claim 9, wherein the nonaqueous electrolytic solution forms a composite interface film composed of an inorganic component, a sulfonyl-containing component and an organic component at an electrode interface.
  17. 17. A secondary battery comprising the nonaqueous electrolytic solution according to any one of claims 9 to 16.
  18. 18. The secondary battery according to claim 17, further comprising a positive electrode and a negative electrode, wherein the positive electrode is selected from one or more of lithium cobaltate, nickel cobalt manganese ternary material, nickel cobalt aluminum ternary material, lithium iron phosphate, lithium manganese iron phosphate, lithium-rich manganese-based material, and/or the negative electrode is a graphite negative electrode material or a graphite/silicon-carbon composite negative electrode material.

Description

Electrolyte additive, nonaqueous electrolyte and secondary battery Technical Field The invention relates to the technical field of electrochemical energy storage, in particular to an electrolyte additive, a non-aqueous electrolyte and a secondary battery thereof. Background With the deep development of lithium ion secondary batteries in the fields of power batteries and large-scale energy storage, improving the stability of electrode interfaces in the high-voltage and long-cycle processes becomes a core challenge, and different types of positive electrode material systems face interface stability problems. For high-voltage systems such as ternary layered oxide, lithium cobaltate and the like, the charge-discharge cycle process is often accompanied by dissolution of transition metal cations, phase change degradation of an active surface, continuous oxidative decomposition of electrolyte on the high-active surface and increase of interface impedance. And for phosphate olivine structural materials such as lithium iron phosphate, lithium manganese iron phosphate and the like, although the structural stability is higher and the thermodynamic stability is higher, the problems of electrolyte interface decomposition product accumulation, uneven interface film formation, rising charge transfer impedance, high rate performance attenuation and the like can still occur in a long cycle at a dynamic level. The existing electrolyte system generally depends on a single additive for interface regulation, and the additive generally lacks definite structural partition and functional division in the electrode surface film forming process, so that the interfacial mechanical stability, the electronic insulation property, the ion conductivity and the oxidation resistance or reduction resistance are difficult to be simultaneously considered in different material systems. Therefore, development of an electrolyte system which can construct an interfacial film with a composite structure on the surface of an electrode in situ through the synergistic effect of various additives is needed to realize targeted and compatible regulation and control of the interfacial characteristics of different cathode materials. Disclosure of Invention In order to solve the technical problems and solve the defects in the prior art, the invention provides an electrolyte additive, a non-aqueous electrolyte and a secondary battery thereof, and an electrolyte system of an interfacial film with a film forming time sequence and a space partition structure is constructed at an electrode interface through a multi-component additive system. The invention is suitable for various positive electrode material systems, and realizes targeted and compatible regulation and control of interface characteristics of different positive electrode materials. To achieve the above object, the present invention provides in a first aspect an electrolyte additive comprising a first additive, a second additive and a third additive; The first additive is lithium salt containing a fluorosulfonyl structure; the second additive is a compound containing a sulfonyl structure; The third additive is a compound containing at least two sulfate ring structural units. In some implementations, the first additive is selected from at least one of lithium fluorosulfonate (LiFSO 3), lithium trifluoromethane sulfonate (LiCF 3SO3), lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethane sulfonyl) imide (LiTFSI). In some implementations, the second additive is a compound containing a sulfonyl fluoride structure. In some implementations, the second additive has a structure as shown in formula (I): (formula I); Wherein R 1 is selected from hydrogen, C 1–C6 alkyl, fluoro C 1–C6 alkyl or C 1–C6 alkyl substituted with cyano, and R 2 is selected from hydrogen, C 1–C6 alkyl or fluoro C 1–C6 alkyl. In some implementations, the second additive is preferably one or more of N, N-dimethyl sulfonyl fluoride, N-methyl-N-ethyl sulfonyl fluoride, N-dicyanosulfonyl fluoride. In some implementations, the third additive is a compound containing at least two 1,3, 2-dioxathiolane-2, 2-dioxide (DTD) structural units. In some implementations, the electrolyte additive further includes a fourth additive that is an interface-modulating additive. In some implementations, the fourth additive is selected from at least one of lithium difluoroborate (LiDFOB), lithium bisoxalato borate (LiBOB), a ethylene carbonate additive (VC), fluoroethylene carbonate (FEC), 1, 3-Propane Sultone (PS), 1,3, 2-dioxathiolane-2, 2-dioxide (single DTD). In a second aspect, the present invention provides a nonaqueous electrolyte comprising the electrolyte additive provided in the first aspect, at least one primary lithium salt, and at least one nonaqueous organic solvent. In some implementations, the mole percent of the first additive is 0.01-0.5% based on 100% of the sum of the molar amounts of the primary lithium salt and the first ad